Backpack



FIG. 1 is a perspective view of a backpack showing my new design;

FIG. 2 is a front view thereof;

FIG. 3 is a rear view thereof;

FIG. 4 is a side view thereof;

FIG. 5 is a second side view thereof;

FIG. 6 is a top view thereof; and,

FIG. 7 is a bottom view thereof.

The broken lines immediately adjacent to the shaded area represent unclaimed boundaries of the design. The unshaded regions, demarcated by broken lines, within or adjacent to the shaded area form no part of the claimed design. The broken lines showing the remainder of the backpack are for environmental purposes only and form no part of the claimed design. 

CLAIM The ornamental design for a backpack, as shown and described. 